testing dial up modem over VoIP

Discussion in 'VOIP' started by Chris Eilersen, Dec 3, 2004.

  1. Is it possible to test a dial up modem connection using a VoIP phone? I'm
    thinking that it's not as I can't seem to get a modem in the house to

    Chris Eilersen, Dec 3, 2004
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  2. Chris Eilersen

    Seeker Guest

    Seeker, Dec 4, 2004
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  3. Chris Eilersen

    stephen Guest

    So IP telephony systems do support modems, but they dont use an IP phone -
    the speech compression system tends to scramble the signal.

    If you had a phone set to do G.711 (which is 64k of data, maybe 80k or more
    with overhead) you may get somewhere, since that is the same digitisation
    used in a conventional TDM pbx - and your modem has to work with that....
    stephen, Dec 4, 2004
  4. Chris Eilersen

    Mitel Lurker Guest

    You can't use a conventional dial-up modem over any compressed VOIP line
    and even G.711 uncompressed is going to be a challenge unless you've got
    voice priority (802.1p/q) working end-to-end.
    Mitel Lurker, Dec 4, 2004
  5. I couldn't even get a modem to work thru a Sipura 3000 going from the POTS
    port out the PSTN port. This is implimented in the Sipura as a VOIP
    connection between the two ports inside the box.

    I've completely given up on being able to connect modems via VOIP.

    Mike Schumann
    Mike Schumann, Dec 11, 2004
  6. Chris Eilersen

    BK80 Guest

    Yes it is possible, but the tricky part is keeping the voIP conenction
    solid enough. Be sure that you are running g711u law and not g729.
    That is the first point to start.
    BK80, Dec 12, 2004
  7. Chris Eilersen

    m Guest

    Well there is also X-lite iLBC ..

    oh and don't forget GSM

    WHat I do not get is why there does not seem to be any hardware phones
    that support them .. beyond professional office phones like Snom..

    (not snom supports GSM but no iLBC yet anyway)

    Anyone know phones that support these two standard codec's .. I figure
    since snom is based on linux and is pretty much a open phone that they
    will support it before the otheres..

    m, Feb 5, 2005
  8. Chris Eilersen


    Mar 25, 2007
    Likes Received:
    Yes, it is.

    I use vonage for my phone service. I have two phone lines and a houseful of computers and networking gear including modems, both internal and external, so I decided to try the impossible: dial into a server over a voip phone line.

    I hooked up a computer with a standard 56k dialup modem running Windows XP (pro) as dialup client, basically I went to Network Connections and used the New Connection Wizard to add my other computer as ISP.

    ‘New Connection Wizard’

    ‘Connect to the Internet’

    ‘Set up my connection manually’

    ‘Connect using a dial-up modem’

    ‘Enter ISP name’

    ‘Enter phone number’

    ‘Enter User name, Password, Confirm password’


    I set up another computer as a server using the same wizard and another standard 56k modem.

    ‘New Connection Wizard’

    ‘Set up an advanced connection’

    ‘Accept incoming connections’

    ‘Devices for Incoming connections’ I chose the modem from the list.

    ‘Do not allow virtual private connections’

    ‘User Permissions’, I chose a username from the list of windows accounts for the server box.

    ‘Networking Software’ I selected Internet Protocol (TCP/IP) and hit properties, unselected “Allow callers to access my local area network” since this was intended to be an internet access dial up connection, not a remote LAN user connection and checked “Allow calling computer to specify its own IP address.


    The I plugged each computers modem into a different voip phone line and dialed.

    They connect just fine about 75% of the time, although speeds vary from 14.4k to 31.2k in my experience so far. Usually it’s around 16-20k connection, it works better if you disable compression in your voip, or at least set the bandwidth as high as possible, I set my vonage settings to 90k in the bandwidth saver feature of my vonage account page. Vonage has a great web interface for managing your account by the way.

    In order to get the client computer to load web pages and find hosts on the internet I had to go back to Network connections and specify the ISP assigned dynamic ip address and dns servers from my cable modem.

    ‘Network Connections’

    ‘Right click on the dial up connection I set up, select properties’

    ‘Click the networking tab’

    ‘select Internet Protocol (TCP/IP)’

    ‘hit properties’

    ‘select “use the following ip address”, enter the public ip of my cable modem connection’

    ‘enter the dns servers from my cable modem connection’

    ‘Click OK’

    ‘Click OK again to finish’

    I dialed up the server side again and started browsing.
    marcus4132, Mar 25, 2007
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